Hydrophobic dissociation assembled

We have seen earlier in this chapter how the self-assembly of casein systems is sensitively affected by temperature. Another thermodynamic variable that can affect protein-protein interactions in aqueous media is the hydrostatic pressure. Static high-pressure treatment causes the disintegration of casein micelles due to the dismption of internal hydro-phobic interactions and the dissociation of colloidal calcium phosphate. This phenomenon has been used to modify the gelation ability of casein without acidification as a consequence of exposure of hydrophobic parts of the casein molecules into the aqueous medium from the interior of the native casein micelles (Dickinson, 2006). High-pressure treatment leads to a reduction in the casein concentration required for gelation under neutral conditions, especially in the presence of cosolutes such as sucrose (Abbasi and Dickinson, 2001, 2002, 2004 Keenan et al., 2001). 

Aqueous micelles are thermodynamically stable and kinetically labile spherical assemblies. Their association-dissociation process is very fast and occurs within milliseconds. The actual order is less than shown in Figure 1. Driving forces for the formation of aqueous micelles or vesicles are the solvation of the headgroup and the desolvation of the alkyl chain ( hydrophobic effect ). Because of the rapid exchange of surfactants, the core of the micelle contains a small percentage of water molecules. Aqueous assemblies are preferentially stabilized by entropy, and reverse micelles by enthalpy [4]. The actual formation of micelles begins above a certain temperature (Krafffs point) and above a characteristic concentration (critical micelle concentration, CMC). Table 1 shows a selection of typical micelle-forming surfactants and their CMCs. 

Functional polymers are macromolecules that have unique properties or uses. The properties of such materials are often determined by the presence of chemical functional groups that are dissimilar to those of the backbone chains. Examples are polar or ionic functional groups on hydrocarbon backbones or hydrophobic groups on polar polymer chains. Chemical heterogeneity on the polymer chains can le to enhanced reactivity, phase separation, or association. The ability of functional polymers to form self-assemblies or supramolecular stmctures is a further incentive. When the formation or dissociation of the self-assemblies is triggered by chemical or physical stimuli so called smart materials can result ... 

Abstract We present an overview of statistical thermodynamic theories that describe the self-assembly of amphiphilic ionic/hydrophobic diblock copolymers in dilute solution. Block copolymers with both strongly and weakly dissociating (pH-sensitive) ionic blocks are considered. We focus mostly on structural and morphological transitions that occur in self-assembled aggregates as a response to varied environmental conditions (ionic strength and pH in the solution). Analytical theory is complemented by a numerical self-consistent field approach. Theoretical predictions are compared to selected experimental data on micellization of ionic/hydrophobic diblock copolymers in aqueous solutions. 

A number of theoretical studies have been devoted to analysis of the self-assembly of amphiphilic ionic/hydrophobic diblock copolymers [13-24]. Most of these studies considered copolymers with strongly dissociating (also referred to as quenched ) PE blocks [13-18, 20] and extensively exploited the analogy between the conformation of PE blocks in a corona and that in a spherical PE brush [25-33] or PE stars (see [10] for a review). The micellization and the responsive behavior of nanostructures formed by copolymers with pH-sensitive PE blocks have also been systematically studied in recent years [19, 21-23]. 

We start with a brief reminder of the theory of self-assembly in a selective solvent of non-ionic amphiphilic diblock copolymers. Here, the focus is on polymorphism of the emerging copolymer nanoaggregates as a function of the intramolecular hy-drophilic/hydrophobic balance. We then proceed with a discussion of the structure of micelles formed by block copolymers with strongly dissociating PE blocks in salt-free and salt-added solutions. Subsequently, we analyze the responsive behavior of nanoaggregates formed by copolymers with pH-sensitive PE blocks. The predictions of the analytical models are systematically complemented by the results of a molecularly detailed self-consistent field (SCF) theory. Finally, the theoretical predictions are compared to the experimental data that exist to date. 

From the perspective of the consilient mechanism, the assembly of filaments as required for muscle contraction and the necessary movement of components within the cell involves hydrophobic association/dissociation between composite subunits. The actin thin filament of... 

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